Lacustrine Plains (or lake plains) are lakes that get filled by incoming sediment. Over time, the water may drain from the lake, leaving the deposited sediments behind. This can be caused by natural drainage, evaporation or other geophysical processes.
The topography of Southern Indiana reflects a system of complex lacustrine plains. An ice sheet during the Illinoian stage changed drainage patterns in the area and formed a series of proglacial lakes. One of the more distinct lakes in this series was Lake Quincy, named for Quincy, Indiana. As the ice sheet withdrew, these lakes disappeared leaving behind the lacustrine plains that are still preserved today. Quincy Lake, in particular, left 30 to 40 foot deep sediments, ranging in composition from gravels to silts.